Micro electro mechanical systems (hereinafter may be sometimes abbreviated to “MEMS”) is applicable to various fields such as a wireless communication field, an optical engineering field, an acceleration sensor field, a bioscience field, and power engineering field. In the power engineering field among the above described fields, a device manufactured based on the MEMS, i.e., an Energy Harvester for collecting and utilizing energy from light, heat, and vibration which are dissipated in environment, has been developed. The Energy Harvester is applied to a power supply of a low-power radio to thereby realize a wireless sensor network which requires no power supply cables and batteries. Application of the MEMS technology to the Energy Harvester enables down-sizing of the Energy Harvester.
In environment where less light and heat can be generated, a vibration power generator is useful since such power generator can generate electric power by utilizing vibration which is generated by members composing an element when force is applied to the members from outside environment. The vibration power generator is divided into a piezoelectric-type vibration power generator, an electromagnetic-type vibration power generator, and an electrostatic-type vibration power generator. The electrostatic-type vibration power generator has an advantage that it requires no piezoelectric material and no magnetic material and thus can be manufactured with a simple manufacturing method.
The electrostatic type vibration power generator is equipped with electrodes facing to electrically charged electrets and is configured such that, when a weight is vibrated due to force applied from the outside environment, a facing area in which the electrets face to the electrodes varies. The electrostatic type vibration power generator is the Energy Harvester which realizes electric power generation by electric power supply and electric power discharge to the electrodes in such a manner that a variation of an electrostatic capacity occurring according to the variation of the facing area is utilized to repetitively generate the maximum value and the minimum value of the electrostatic capacity. Various electrostatic-type vibration power generators have been proposed to date.